Electronic terminal, input correction method, and program

ABSTRACT

An information processing apparatus that includes a first sensor that receives a first type of signal; second and third sensors that receive a second type of signal; a control unit that calculates a position of a source from which a signal of the first type and a signal of the second type are transmitted based on a first time at which the signal of the first type is received at the first sensor, a second time at which the signal of the second type is received at the second sensor and a third time at which the signal of the second type is received at the third sensor; and a display that displays an image corresponding to a path obtained based on changes in position of the source calculated by the control unit.

CROSS REFERENCE TO RELATED APPLICATION

The present application claims the benefit of the earlier filing date ofU.S. Provisional Patent Application Ser. No. 61/498,805 filed on Jun.20, 2011, the entire contents of which is incorporated herein byreference.

BACKGROUND

1. Field of the Disclosure

The present disclosure relates to an electronic terminal including adisplay unit, an input correction method performed in the electronicterminal, and a program for achieving the input correction method.

2. Description of Related Art

Various processing operations of electronically reading a picture or acharacter handwritten on paper or the like to obtain image data orcharacter data have been performed.

In this case, a method of preparing an input pen designed forhandwriting detection as a writing implement and causing a receiver nearthe input pen to detect handwriting obtained by the movement of theinput pen on paper is actually used.

For example, Japanese Unexamined Patent Application Publication No.2006-309474 describes an example in which an input pen is configured tooutput an infrared signal and an ultrasonic signal from a leading endthereof at the same time and a receiver disposed near the input penreceives the infrared signal and the ultrasonic signal and detectshandwriting. In this case, the receiver performs processing fordetecting the position of the leading end of the pen on the basis of thedifference between a time at which the infrared signal is received and atime at which the ultrasonic signal is received. By repeatedlyperforming this position detection processing at short intervals, thechange in the position of the leading end of the pen is detected andhandwriting is detected.

Any handwriting detection receiver having a function of receiving aninfrared signal and an ultrasonic signal may be used. For example, whena radiotelephone terminal called smartphone has a function of receivingan infrared signal and an ultrasonic signal, the radiotelephone terminalcan have a handwriting detection function.

SUMMARY

In the above-described detection of handwriting input by an input penwhich is performed using an infrared signal and an ultrasonic signal, itis necessary to reduce the change in positional relationship betweenpaper on which writing is performed and a receiver. That is, inprocessing for detecting handwriting input by an input pen using aninfrared signal and an ultrasonic signal, when a receiver is moved, arelative position to be detected is changed and a handwriting detectioncondition is disturbed. This is caused because relative positions of theinput pen and the receiver are detected in the handwriting detectionprocessing.

When the handwriting detection condition is disturbed by the change inthe position of the receiver, it is difficult to accurately detecthandwriting. Detected handwriting differs from a picture or a characteractually written on paper with an input pen.

It is an object of the present disclosure to appropriately detecthandwriting even when the relative positions of a writing implement fortransmitting a signal and a receiver for receiving the signaltransmitted from the writing implement at a position near the writingimplement are changed.

According to a first embodiment, the disclosure is directed to aninformation processing apparatus that includes a first sensor thatreceives a first type of signal; second and third sensors that receive asecond type of signal; a control unit that calculates a position of asource from which a signal of the first type and a signal of the secondtype are transmitted based on a first time at which the signal of thefirst type is received at the first sensor, a second time at which thesignal of the second type is received at the second sensor and a thirdtime at which the signal of the second type is received at the thirdsensor; and a display that displays an image corresponding to a pathobtained based on changes in position of the source calculated by thecontrol unit.

According to another exemplary embodiment, the disclosure is directed toa method performed by an information processing apparatus. The methodincluding receiving a first type of signal transmitted from a source ata first sensor at a first time; receiving a second type of signaltransmitted from a source at a second sensor at a second time; receivingthe second type of signal transmitted from the source at a third sensorat a third time; calculating a position of the source based on the firsttime, the second time, and the third time; and displaying an imagecorresponding to a path obtained based on changes in position of thesource calculated by the control unit.

According to another exemplary embodiment, the disclosure is directed toa non-transitory computer-readable medium including computer programinstructions, which when executed by an information processingapparatus, causes the information processing apparatus to perform amethod. The method including receiving a first type of signaltransmitted from a source at a first sensor at a first time; receiving asecond type of signal transmitted from a source at a second sensor at asecond time; receiving the second type of signal transmitted from thesource at a third sensor at a third time; calculating a position of thesource based on the first time, the second time, and the third time; anddisplaying an image corresponding to a path obtained based on changes inposition of the source calculated by the control unit.

According to the present disclosure, even when an apparatus forreceiving a signal of a first type and a signal of a second type ismoved, it is possible to continuously perform correct handwritingdisplay without disturbing the detected position of a writing implementsince correction processing is performed.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a perspective view illustrating an example of a systemaccording to an embodiment of the present disclosure.

FIG. 2 is a block diagram illustrating an exemplary configuration of anelectronic terminal according to an embodiment of the presentdisclosure.

FIG. 3 is a block diagram illustrating an exemplary configuration of awriting implement according to an embodiment of the present disclosure.

FIG. 4 is a diagram describing an example of a usage pattern accordingto an embodiment of the present disclosure.

FIG. 5 is a flowchart illustrating an example of a correction processaccording to an embodiment of the present disclosure.

FIG. 6 is a diagram describing a display example of touch points at thetime of correction according to an embodiment of the present disclosure.

FIG. 7 includes diagrams describing an exemplary case at the time ofstart of a correction process according to an embodiment of the presentdisclosure.

FIG. 8 includes diagrams describing an exemplary case at the time of acorrection process according to an embodiment of the present disclosure.

FIG. 9 is a flowchart illustrating an example of a distance measurementprocess according to an embodiment of the present disclosure.

FIG. 10 is a diagram describing a display example of a distanceaccording to an embodiment of the present disclosure.

FIG. 11 is a perspective view illustrating an exemplary configuration ofan electronic terminal according to another embodiment of the presentdisclosure.

DETAILED DESCRIPTION

An exemplary embodiment of the present disclosure will be described inthe following order.

-   1. Exemplary Entire Configuration of System (FIG. 1)-   2. Exemplary Configuration of Electronic Terminal (FIG. 2)-   3. Exemplary Configuration of Writing Implement (FIG. 3)-   4. Example of Usage Pattern (FIG. 4)-   5. Description of Correction Process (FIGS. 5 to 8)-   6. Description of Distance Display Process (FIGS. 9 and 10)-   7. Modification (FIG. 11)    1. Exemplary Entire Configuration of System

FIG. 1 is a diagram illustrating an example of a system according to anembodiment of the present disclosure (hereinafter referred to as “thisexample”).

In this example, as illustrated in FIG. 1, an electronic terminal 100and an input pen 200 are prepared. The electronic terminal 100 is aradiotelephone terminal called smartphone whose functionality can beincreased by installing various pieces of application software into theradiotelephone terminal. On the surface of a casing 101 of theelectronic terminal 100, a display unit 102 that is a relatively largedisplay panel is disposed. As the display unit 102, a display devicesuch as a liquid crystal display panel or an organic electroluminescence(EL) display panel is used.

On the surface of the electronic terminal 100, operation keys includedin an operation unit 119, a call speaker 121, and a microphone 122 arefurther disposed.

On a side surface 101 a of the casing 101 of the electronic terminal100, three sensors 111, 112, and 113 are aligned in a substantiallylinear array. That is, at the substantially center of the side surface101 a, the infrared sensor 111 for receiving an infrared signal isdisposed. The first ultrasonic sensor 112 is disposed at a positionapart from the infrared sensor 111 by a predetermined distance on theleft side of the infrared sensor 111. The second ultrasonic sensor 113is disposed at a position apart from the infrared sensor 111 by apredetermined distance on the right side of the infrared sensor 111. Thedistance between the infrared sensor 111 and each of the ultrasonicsensors 112 and 113 is, for example, several centimeters.

The input pen 200 is a writing implement such as a ballpoint pen usedfor writing on paper near the electronic terminal 100. A pen tip switch202 is disposed at a leading end 201 of the input pen 200. When theleading end of the pen is brought into contact with paper or the like,the pen tip switch 202 is turned on. Inside the leading end 201 of theinput pen 200, an infrared transmission unit 211 and an ultrasonicoscillation unit 212 are disposed. During the pen tip switch 202 is inan ON state, the infrared transmission unit 211 periodically transmitsan infrared signal and the ultrasonic oscillation unit 212 periodicallyoscillates an ultrasonic signal. The transmission of an infrared signaland the oscillation of an ultrasonic signal are performed at the sametime.

There is a mode in which the measurement of the position of the leadingend of the pen is continued by continuously transmitting an infraredsignal and an ultrasonic signal regardless of whether the pen tip switchis in the ON or OFF state. As a method of notifying a body ofinformation about the ON or OFF state of the pen tip switch, a method ofchanging the frequencies of an infrared signal and an ultrasonic signalmay be used.

As illustrated in FIG. 1, an infrared signal IR1 transmitted from theinput pen 200 is detected by the infrared sensor 111 in the electronicterminal 100. An ultrasonic signal SW1 oscillated by the input pen 200is detected by the first ultrasonic sensor 112 and the second ultrasonicsensor 113 in the electronic terminal 100.

The infrared signal IR1 and the ultrasonic signal SW1 are output fromthe input pen 200 at the same time. However, since speeds at which thesesignals are transmitted in space differ from each other, the ultrasonicsignal SW1 is detected by the two ultrasonic sensors 112 and 113 afterthe infrared signal IR1 has been detected by the infrared sensor 111. Onthe basis of the detection time difference between the infrared signalIR1 and the ultrasonic signal SW1, the distance between the input pen200 and the side surface 101 a of the electronic terminal 100 isdetermined.

In accordance with the position of the input pen 200, the time at whichthe ultrasonic signal SW1 is detected by the first ultrasonic sensor 112and the time at which the ultrasonic signal SW1 is detected by thesecond ultrasonic sensor 113 are changed. When the ultrasonic signal SW1is detected by the two ultrasonic sensors 112 and 113 at the same time,the two ultrasonic sensors 112 and 113 are at the same distance from theinput pen 200. On the other hand, when the ultrasonic signal SW1 isdetected by the two ultrasonic sensors 112 and 113 at different times,there is a difference in the distance from the input pen 200 between thetwo ultrasonic sensors 112 and 113 which is changed in accordance withthe time difference.

Accordingly, the position of the leading end of the input pen 200 asviewed from the electronic terminal 100 is calculated on the basis ofthe difference between a time at which the infrared signal IR1 isdetected and a time at which the ultrasonic signal SW1 is detected andthe difference between times at which the ultrasonic signal SW1 isdetected by the two ultrasonic sensors 112 and 113.

By detecting the infrared signal IR1 and the ultrasonic signal SW1output from the leading end 201 of the input pen 200 at periodicintervals (e.g. several tens of times per second), the position of theleading end of the pen is detected at short intervals. By connecting thepositions that have been detected at short intervals and generating acontinuous line, handwriting recorded on paper with the input pen 200 isdetected. The detected handwriting is displayed on the display unit 102and is stored in the electronic terminal 100 as image data.

2. Exemplary Configuration of Electronic Terminal

Next, an exemplary configuration of the electronic terminal 100 will bedescribed with reference to a block diagram in FIG. 2.

The electronic terminal 100 includes a communication processing unit 115for performing radio processing as a radiotelephone terminal. An antenna116 is connected to the communication processing unit 115, and thecommunication processing unit 115 performs radio communication with aradiotelephone base station via the antenna 116. The communicationprocessing unit 115 performs speech communication and data communicationunder the control of the control unit 117. For example, at the time ofspeech communication, transmission data and receiving data aretransmitted between the communication processing unit 115 and the speechprocessing unit 120, and communication is performed using the speaker121 and the microphone 122 connected to the speech processing unit 120.At the time of data communication, a memory 118 stores data received bythe communication processing unit 115, and an image and text aredisplayed on the display unit 102 on the basis of display data.Transmission data stored in the memory 118 is wirelessly transmittedfrom the communication processing unit 115.

As illustrated in FIG. 1, the electronic terminal 100 includes theinfrared sensor 111, the first ultrasonic sensor 112, and the secondultrasonic sensor 113, and supplies data detected by each of thesesensors to the control unit 117 via an internal bus line. The infraredsensor 111 is a sensor functioning as a receiving unit for receiving aninfrared signal transmitted from the input pen 200. The first ultrasonicsensor 112 and the second ultrasonic sensor 113 are sensors functioningas receiving units for receiving an ultrasonic signal transmitted fromthe input pen 200.

The control unit 117 performs processing for calculating the position ofthe input pen 200 on the basis of pieces of data of detection performedby the sensors 111, 112, and 113. When the control unit 117 calculatesthe position of the input pen 200, data of handwriting obtained by thechange in the calculated position is stored in the memory 118 and isdisplayed on the display unit 102. This storage processing and thisdisplay processing are performed by causing the control unit 117 toexecute a program (software) stored in the memory 118.

The infrared sensor 111 and the ultrasonic sensors 112 and 113 may beused in an application other than the detection of the position of theinput pen 200. For example, using the infrared sensor 111, theelectronic terminal 100 may perform data communication with anotherterminal near the electronic terminal 100.

The electronic terminal 100 further includes an acceleration sensor 114that is an acceleration detection unit for detecting accelerationapplied to the electronic terminal 100, and supplies data of detectionperformed by the acceleration sensor 114 to the control unit 117. Thecontrol unit 117 detects the movement of the electronic terminal 100 onthe basis of the supplied data of acceleration detection.

The operation unit 119 included in the electronic terminal 100 sets anoperation mode performed by the control unit 117. For example, theoperation unit 119 can set a mode in which storage and display ofhandwriting input with the input pen 200 are performed. Furthermore, theoperation unit 119 can set a reset mode in which a terminal position isreset. This reset mode will be described later.

A display panel with a touch panel may be used as the display unit 102included in the electronic terminal 100, and the operation unit 119 mayoutput an operation instruction when a touch operation performed on thedisplay panel is detected.

3. Exemplary Configuration of Writing Implement

Next, the configuration of the input pen 200 that is a writing implementwith which a user performs writing by hand will be described withreference to FIG. 3.

The input pen 200 includes the pen tip switch 202 that is turned on whena writing operation is performed on paper or the like. When the controlunit 213 detects that the pen tip switch 202 has been turned on, thetransmission of an infrared signal from the infrared transmission unit211 and the oscillation of an ultrasonic signal from the ultrasonicoscillation unit 212 are periodically performed in conjunction with eachother. When the pen tip switch 202 is turned off, the control unit 213terminates the transmission of an infrared signal from the infraredtransmission unit 211 and the oscillation of an ultrasonic signal fromthe ultrasonic oscillation unit 212.

Although not illustrated in FIG. 3, the input pen 200 further has afunction of a typical writing implement such as a ballpoint pen.

4. Example of Usage Pattern

FIG. 4 illustrates an example of a usage pattern of the input pen 200and the electronic terminal 100 when a handwriting input is performedwith the input pen 200 and the electronic terminal 100.

In the example illustrated in FIG. 4, a user draws a certain picture(figure) on a notebook 300 with the input pen 200 held by a hand H.

On the upper side of the notebook 300, the electronic terminal 100 isdisposed. At that time, the electronic terminal 100 is placed so thatthe side surface 101 a on which the sensors 111, 112, and 113 aredisposed faces the notebook 300.

When a handwriting display mode is set in the electronic terminal 100 inthe state illustrated in FIG. 4, the electronic terminal 100 detectshandwriting input with the input pen 200. Accordingly, the electronicterminal 100 detects handwriting of a picture 301 that a user hashandwritten on the notebook 300 with the input pen 200, and an image 102a that is the same as the picture 301 is displayed on the display unit102. In the example illustrated in FIG. 4, the image 102 a displayed onthe display unit 102 is a reduced image of the picture 301 that has beenhandwritten.

When the electronic terminal 100 according to this example is movedwhile performing handwriting detection illustrated in FIG. 4, theelectronic terminal 100 performs processing for correcting the positionthereof relative to the input pen. When the control unit 117 determinesthat acceleration larger than a predetermined threshold value has beendetected on the basis of data of detection performed by the accelerationsensor 114 (FIG. 2) included in the electronic terminal 100, a programfor position correction processing is started. When the operation unit119 included in the electronic terminal 100 sets the reset mode, theprogram for position correction processing can also be started.

5. Description of Correction Process

FIG. 5 is a flowchart illustrating a position correction processperformed under the control of the control unit 117.

First, the control unit 117 performs processing for calculating theposition of the input pen 200 in the handwriting display mode. In astate in which the storage and display of handwriting input at thedetected position are performed (step S11), acceleration detectionprocessing is performed on the basis of the output of the accelerationsensor 114 and it is determined whether acceleration larger than athreshold value has been detected (step S12). When acceleration largerthan the threshold value is not been detected, it is determined whetheran operation of setting a reset mode has been performed (step S13). Whenthe operation of setting the reset mode is not performed, the processreturns to step S11 in which the storage and display of handwriting iscontinuously performed. It is assumed that the storage and display ofhandwriting in step S11 is performed in an exemplary state illustratedin FIG. 4 in which writing is performed on the notebook 300 with theinput pen 200.

When it is determined in step S12 that acceleration larger than thethreshold value has been detected and it is determined in step S13 thatthe operation of setting the reset mode has been performed, the processproceeds to step S14 in which the detection and storage of writinginformation are terminated and the reset mode is started.

When the reset mode is started, the control unit 117 determines a firstsingular point (hereinafter referred to as a point A) on a currentwriting image displayed in step S11 and displays an image on which thepoint A is identifiable on the display unit 102 (step S15). At thattime, for example, it is desired that a mark indicating the point A anda character or sign encouraging a user to touch the point A with theinput pen 200 be displayed on the image.

When a user sees the displayed image, the user checks the point A on thedisplayed image, searches the picture 301 on the notebook 300 for thepoint A, and touches the point A with the leading end of the input pen200.

The control unit 117 included in the electronic terminal 100 waits untilan infrared signal and an ultrasonic signal transmitted from the inputpen 200 are detected. When an infrared signal and an ultrasonic signaltransmitted from the input pen 200 are detected, the process proceeds(step S16).

Next, the control unit 117 determines a second singular point(hereinafter referred to as a point B) on a currently displayed writingimage and displays an image on which the point B is identifiable on thedisplay unit 102 (step S17). In this case, it is also desired that acharacter or sign encouraging a user to touch the point B with the inputpen 200 be displayed on the image.

When a user sees the displayed image, the user checks the point B on thedisplayed image, searches the picture 301 on the notebook 300 for thepoint B, and touches the point B with the leading end of the input pen200.

The control unit 117 included in the electronic terminal 100 waits untilan infrared signal and an ultrasonic signal transmitted from the inputpen 200 are detected. When an infrared signal and an ultrasonic signaltransmitted from the input pen 200 are detected, the process proceeds(step S18).

Next, the position of the leading end of the input pen 200 detected instep S16 is registered as the point A in the displayed image, theposition of the leading end of the input pen 200 detected in step S18 isregistered as the point B in the displayed image, and processing forcorrecting a detected position is performed (step S19).

When it is determined that the picture 301 on the notebook 300 has beenrotated as viewed from the electronic terminal 100 in the positioncorrection in step S19, the image displayed on the display unit 102 isrotated by the rotation angle of the picture 301 (step S20). Thus, evenafter correction, the horizontal and vertical directions of the picture301 on the notebook 300 and the horizontal and vertical directions ofthe image 102 a displayed on the display unit 102 are made to conform toeach other.

After the rotation of the image has been performed in step S20, thereset mode ends and the process returns to step S11 in which handwritinginput with the input pen 200 is detected and the storage and display ofthe detected handwriting are performed in the handwriting display mode.In the handwriting display mode after the reset mode, position detectionreflecting the position correction in step S19 is performed.

Next, an example of processing for setting the point A in step S15 inthe flowchart illustrated in FIG. 5 and an example of processing forsetting the point B in step S17 in the flowchart illustrated in FIG. 5will be described with reference to FIG. 6.

FIG. 6 is a diagram illustrating an image 102 b that is input by a penand is displayed on the display unit 102. On the image 102 b in FIG. 6,characters are displayed.

As illustrated in FIG. 6, on the displayed image, an X direction(horizontal direction) and a Y direction (vertical direction) are set.At that time, a substantially center of the displayed image, that is, anintersection of an X directional axis and a Y directional axisillustrated in FIG. 6, is set as an origin at which an evaluation valueis 0. The farther from the origin in the X and Y directions, the largerthe evaluation value. On the left side of the origin in the X directionand the lower side of the origin in the Y direction, the evaluationvalue becomes negative. The X directional axis and the Y directionalaxis are illustrated in FIG. 6 to describe the evaluation value, and arenot actually displayed on an image on the display unit 102.

The control unit 117 checks a value obtained by adding an evaluationvalue in the X direction and an evaluation value in the Y direction ateach pixel on a displayed line corresponding to handwriting on the image102 b, sets a point at which the maximum value is obtained as a point Pathat is the point A, and sets a point at which the minimum value isobtained as a point Pb that is the point B. Accordingly, in the examplein FIG. 6, the upper right end and the lower left end of handwriting inthe image are the points A and B, respectively.

In the example in FIG. 6, in order to make the points A and Bidentifiable, the character of A in a circle and the character of B in acircle are displayed at corresponding positions.

The evaluation value determination processing illustrated in FIG. 6 ismerely an example, and another processing for determining the points Aand B may be performed. For example, an evaluation value in only one ofthe X direction and the Y direction may be used, and a point at whichthe maximum evaluation value is obtained and a point at which theminimum evaluation value is obtained may be set as the points A and B,respectively.

For example, when the evaluation value in the Y direction is used, theupper end and the lower end of handwriting are the points A and B,respectively. When the evaluation value in the X direction is used, theright end and the left end of handwriting are the points A and B,respectively.

These evaluation values may not be used, and randomly selected twopoints on a line corresponding to handwriting on an image may be set asthe points A and B. In this case, it is desired that the points A and Bbe apart from each other by a certain distance.

Alternatively, when there is a single (independent) point or theintersection of a plurality of lines in handwriting on an image, theindependent point or the intersection may be selected as the point A orB. By selecting the independent point or the intersection, a user caneasily check the position of the point and points an input pen at thepoint. For example, a point on the upper side of “i” or the intersectionof a vertical line and a horizontal line of “t” may be set as the pointA or B.

Exemplary cases in which correction processing in the reset modedescribed with reference to the flowchart in FIG. 5 is actuallyperformed will be described with reference to FIGS. 7 and 8.

FIG. 7A illustrates an exemplary case in which the electronic terminal100 is placed on the far side of the notebook 300, an image 102 c thatis the same as a picture 302 drawn on the notebook 300 with the inputpen 200 is displayed on the display unit 102, and the displayed image isstored.

It is assumed that a hand H of a user holding the input pen 200 isbrought into contact with the electronic terminal 100 and the electronicterminal 100 is obliquely moved as illustrated in, for example, FIG. 7Bin a state the display and storage of handwriting illustrated in FIG. 7Aare performed. At that time, the movement of the electronic terminal 100is detected on the basis of data of detection performed by theacceleration sensor 114 in the electronic terminal 100 and the resetmode is set.

When the electronic terminal 100 is moved slightly or very slowly, thereset mode may not be set on the basis of data of accelerationdetection. In such a case, the reset mode may be compulsorily set by auser's operation.

FIG. 8 is a diagram illustrating an exemplary case after the reset modehas been set.

When the reset mode is set, the point Pa (the point A) is displayed onthe image 102 c on the display unit 102 as illustrated in FIG. 8A. Auser sees the position of the point Pa (the point A), determines theposition of the point Pa (the point A) on the picture 302 on thenotebook 300, and touches a determined point 302 a with the leading endof the input pen 200.

After the point A has been touched, the point Pb (the point B) isdisplayed on the image 102 c on the display unit 102 as illustrated inFIG. 8B. The user sees the position of the point Pb (the point B),determines the position of the point Pb (the point B) on the picture 302on the notebook 300, and touches a determined point 302 b with theleading end of the input pen 200.

When the touches of the points A and B illustrated in FIGS. 8A and 8Bhave been completed, a corrected position is calculated in theelectronic terminal 100. After the corrected position has beencalculated and correction has been performed, the handwriting of thepicture 302 handwritten on the notebook 300 with the input pen 200 iscontinuously detected by the electronic terminal 100 and newly inputhandwriting is added to a displayed image 102 d as illustrated in FIG.8C.

By performing the image rotation processing in step S20 in the flowchartillustrated in FIG. 5, the picture 301 on the notebook 300 and thedisplayed image 102 d remain parallel even if the electronic terminal100 is obliquely moved as illustrated in FIG. 8C. The image rotationprocessing in step S20 may not be performed.

On the image 102 c including the point A in FIG. 8A and the image 102 cincluding the point B in the FIG. 8B, the portions of these imagessurrounding points A and B may be enlarged to make the selection ofthese points clearer for the user.

As described previously, when the electronic terminal 100 according tothis example is moved by some impact during detection of the positionthereof relative to the input pen 200 and storage and display of ahandwriting image written with the input pen 200, the correction mode isautomatically set. Accordingly, since correction processing isautomatically started, detection of the relative position can becontinuously performed under the same condition. A handwriting detectioncondition is not therefore disturbed by the movement of the electronicterminal 100.

In the processing for determining two points to be touched by a user atthe time of the correction processing, as illustrated in, for example,the example in FIG. 6, it is possible to automatically select pointseasily recognizable to the user using evaluation values in thehorizontal and vertical directions which are obtained on a linecorresponding to handwriting.

Furthermore, as illustrated in FIG. 8C, it is possible to keep a pictureor a character string being written with the input pen 200 and an imagedisplayed on the electronic terminal 100 parallel to each other byrotating the displayed image on the basis of a state of correction ofthe relative position.

6. Description of Distance Display Process

Next, a process for measuring the distance between certain two pointsand displaying the distance using the electronic terminal 100 accordingto this example and the input pen 200 in a measurement mode will bedescribed.

The process in the measurement mode is performed in accordance with aprocedure illustrated in a flowchart in FIG. 9 under the control of thecontrol unit 117.

First, the control unit 117 determines whether the measurement mode hasbeen set by the operation unit 119 (step S21). When the measurement modeis not set, the control unit 117 waits until the measurement mode isset. When it is determined that the measurement mode has been set, it isdetermined whether a first point that is a measurement starting pointhas been touched by the input pen 200 (step S22). When it is determinedthat the touch of the first point has been detected, the detected pointis set as a starting point (step S23).

Subsequently, it is determined whether a second point that is ameasurement end point has been touched by the input pen 200 (step S24).When it is determined that the touch of the second point has beendetected, the detected point is set as an end point (step S25). Thedistance between the starting point and the end point is determined, andthe determined distance is displayed on the display unit 102 (step S26).

FIG. 10 is a diagram illustrating an example of a processing state inthe measurement mode.

For example, as illustrated in FIG. 10, it is assumed that a specificpoint 311 in a figure written on the notebook 300 is set as a startingpoint and another specific point 312 is set as an end point. At thattime, the electronic terminal 100 detects the positions of these pointsand calculates the distance between the positions.

In the example illustrated in FIG. 10, a scale image 102 f is displayedon the display unit 102 in the electronic terminal 100 and the scaleimage 102 f indicates the calculated distance.

Thus, it is possible to measure the distance between certain two pointsand display the measured distance using a position detection function ofthe electronic terminal 100. The electronic terminal 100 functions as anelectronic measuring device. A distance is presented in a scale in theexample in FIG. 10, but may be numerically represented.

7. Modification

In the example illustrated in FIG. 1, the casing 101 of the electronicterminal 100 contains the sensors 111, 112, and 113. A casing containingthe sensors 111, 112, and 113 and the body of the electronic terminal100 may be separately formed.

For example, as illustrated in FIG. 11, in an electronic terminal 100′,an adaptor connection unit 131 is formed on the side surface of a casingand a receiving adaptor 400 is connected to the adaptor connection unit131. The electronic terminal 100′ is the same as the electronic terminal100 illustrated in FIG. 2 except that the infrared sensor 111, the firstultrasonic sensor 112, and the second ultrasonic sensor 113 are notdisposed and the adaptor connection unit 131 is disposed.

An infrared sensor 401, a first ultrasonic sensor 402, and a secondultrasonic sensor 403 are disposed in the receiving adaptor 400illustrated in FIG. 11. The detection outputs of the sensors 401, 402,and 403 are supplied to the electronic terminal 100′. For example, powerfor the sensors 401, 402, and 403 in the receiving adaptor 400 aresupplied from the electronic terminal 100′ via the adaptor connectionunit 131.

In the electronic terminal 100′, the position of a leading end of aninput pen is calculated on the basis of pieces of detection dataacquired by the sensors 401, 402, and 403 in the receiving adaptor 400and correction processing is started when acceleration detected in theelectronic terminal 100′ exceeds a threshold value.

Using the configuration illustrated in FIG. 11, this example can beapplied to an electronic terminal including no infrared sensor and noultrasonic sensor and versatility can be increased.

The position calculation processing may be performed in the receivingadaptor when each sensor performs detection, and data of the calculatedposition may be transmitted to an electronic terminal. In this case,when an acceleration sensor in the electronic terminal detects thatacceleration has exceeded a threshold value, the electronic terminal maytransmit an instruction for setting a reset mode to the receivingadaptor and processing in the reset mode may be performed in thereceiving adaptor.

In the above-described examples, a radiotelephone terminal is used as anelectronic terminal. A configuration and processing according to thepresent disclosure may be applied to various electronic terminals suchas an electronic terminal having a function of reproducing music orvideo for portable devices and an electronic terminal having a functionof playing a video game. Alternatively, a handwriting input apparatushaving only a function of detecting handwriting using a writingimplement such as an input pen may be used.

Each sensor may be disposed in a general-purpose information processingapparatus such as a personal computer apparatus, the output of thesensor may be processed in the information processing apparatus, andsimilar processing may be performed by executing a program (software)for correction processing installed in the general-purpose informationprocessing apparatus.

When the radiotelephone terminal illustrated in FIG. 2 is employed, aprogram using detection data acquired by each sensor may be externallysupplied to the radiotelephone terminal and processing according to thepresent disclosure may be performed in accordance with the program.

In the above-described description, in order to detect the position ofan input pen, an infrared signal and an ultrasonic signal aretransmitted from the input pen. Other types of signals may be used. Thatis, two types of signals having different transmission speeds may beused in combination. For example, an infrared signal and a radio signalin the range of several GHz to several hundred MHz may be used incombination. Alternatively, instead of an infrared signal, a visiblelight signal may be used.

In the correction process illustrated in the flowchart in FIG. 5, thereset mode is started when acceleration is applied to a terminal or auser's operation is performed. Only one of these conditions may be usedas the reset mode start condition. For example, only when accelerationis applied to a terminal, the reset mode may be started. Alternatively,only when a user's operation is performed, the reset mode may bestarted.

The input pen 200 illustrated in FIGS. 1 and 3 is merely an example.Various writing implements can be used under the condition that theyhave a function of transmitting two types of signals to a terminal.

The invention claimed is:
 1. An information processing apparatuscomprising: a first sensor that receives a first type of signal; asecond sensor that receives a second type of signal; a third sensor thatreceives the second type of signal; an acceleration sensor that detectsan acceleration externally applied to the information processingapparatus; and circuitry configured to calculate a position of a sourcefrom which a signal of the first type and a signal of the second typeare transmitted based on a first time at which the signal of the firsttype is received at the first sensor, a second time at which the signalof the second type is received at the second sensor and a third time atwhich the signal of the second type is received at the third sensor;control a display to display an image corresponding to a path obtainedbased on changes in position of the source; and perform correctionprocessing to correct a position of the information processing apparatusrelative to the source by controlling the display to sequentiallydisplay a first mark and a second mark on the image displayed by thedisplay when it is determined that an output of the acceleration sensorexceeds a predetermined threshold value.
 2. The information processingapparatus of claim 1, wherein the first sensor is an infrared sensorthat receives an infrared signal transmitted from the source.
 3. Theinformation processing apparatus of claim 1, wherein the second sensorand the third sensor are ultrasonic sensors that receive an ultrasonicsignal transmitted from the source.
 4. The information processingapparatus of claim 1, wherein the information processing apparatus is amobile terminal including a housing having top, bottom and sidesurfaces.
 5. The information processing apparatus of claim 4, whereinthe first sensor is located substantially in a center of a side surfaceof the housing.
 6. The information processing apparatus of claim 5,wherein the second and third sensors are located on the side surface ofthe housing on opposite sides of the first sensor and at equal distancesfrom the first sensor.
 7. The information processing apparatus of claim1, wherein the circuitry is configured to calculate the position basedon a difference between the first time and the second or third times,and a difference between the second and third times.
 8. The informationprocessing apparatus of claim 1, wherein the circuitry is configured tocompare the output of the acceleration sensor to the predeterminedthreshold value.
 9. The information processing apparatus of claim 1,wherein upon displaying the first mark a next position calculated by thecircuitry is registered as a first position corresponding to the firstmark.
 10. The information processing apparatus of claim 9, wherein upondisplaying the second mark a next position calculated by the circuitryis registered as a second position corresponding to the second mark. 11.The information processing apparatus of claim 10, wherein the circuitryis configured to control the display to rotate the displayed image basedon the first position corresponding to the first mark and the secondposition corresponding to the second mark.
 12. The informationprocessing apparatus of claim 1, wherein the first mark and the secondmark are selected from among points on the path in the displayed imageand correspond to an evaluation value in a horizontal direction and anevaluation value in a vertical direction.
 13. The information processingapparatus of claim 1, wherein the first mark and the second mark arerandomly selected points on the path in the displayed image.
 14. Theinformation processing apparatus of claim 1, wherein the circuitry isconfigured to control the display to display an image indicating adistance between two points.
 15. An information processing apparatuscomprising: a first sensor that receives a first type of signal; asecond sensor that receives a second type of signal; a third sensor thatreceives the second type of signal; circuitry configured to calculate aposition of a source from which a signal of the first type and a signalof the second type are transmitted based on a first time at which thesignal of the first type is received at the first sensor, a second timeat which the signal of the second type is received at the second sensorand a third time at which the signal of the second type is received atthe third sensor; and control the display to display a measurement valuecorresponding to a difference between a first calculated position of thesource and a second calculated position of the source.
 16. A methodperformed by an information processing apparatus, the method comprising:receiving a first type of signal transmitted from a source at a firstsensor at a first time; receiving a second type of signal transmittedfrom a source at a second sensor at a second time; receiving the secondtype of signal transmitted from the source at a third sensor at a thirdtime; calculating a position of the source based on the first time, thesecond time, and the third time; and controlling a display to display ameasurement value corresponding to a difference between a firstcalculated position of the source and a second calculated position ofthe source.
 17. A non-transitory computer-readable medium includingcomputer program instructions, which when executed by an informationprocessing apparatus, causes the information processing apparatus toperform a method, the method comprising: receiving a first type ofsignal transmitted from a source at a first sensor at a first time;receiving a second type of signal transmitted from a source at a secondsensor at a second time; receiving the second type of signal transmittedfrom the source at a third sensor at a third time; calculating aposition of the source based on the first time, the second time, and thethird time; and controlling a display to display a measurement valuecorresponding to a difference between a first calculated position of thesource and a second calculated position of the source.